This invention relates to a data reception apparatus and a data reception method for use with a communication terminal of a digital portable telephone system, for example.
Recently, a CDMA (code division multiple access) system has been available as a wireless connection system for connecting a base station and communication terminals comprising a digital portable telephone system via radio waves.
The CDMA portable telephone system has hitherto been standardized under the title of IS-95 by TIA (Telecommunications Industry Association). According to the standardization of the TIA under the title of IS-95, it is standardized that the CDMA portable telephone system uses a transfer rate (hereinafter referred to as xe2x80x9cline transfer ratexe2x80x9d) of one kind (e.g. approximately 19200 bps) in the wireless interval between the base station and the communication terminal. It is also standardized that, when data is transmitted within the communication terminal of the CDMA portable telephone system, such communication terminal selects a proper data transfer rate corresponding to a line quality, a data quality and the like from a plurality of kinds of data transfer rates (e.g. four kinds of data transfer rates of approximately 9600 bps, approximately 4800 bps, approximately 2400 bps and approximately 1200 bps) comprising line transfer rates of a reciprocal of an integer of the line transfer rate, i.e. 1/n (n is an arbitrary integer) of the line transfer rate and uses such selected data transfer rate.
When the communication terminal of the CDMA portable telephone system intends to transmit data, since data amounts of transmission object data differ at every available data transfer rate, the communication terminal processes transmission object data in the manner different at every data transfer rate so that transmission object data comprising respective data transfer rates may be converted into data the data amounts of which are the same apparently. Then, the communication terminal becomes able to transmit these data at one kind of line transfer rate. Therefore, when the communication terminal receives data transmitted from other communication terminal through the base station, the communication terminal has to process the received data in the manner corresponding to the above-described used data transfer rate.
When the communication terminal transmits data, data is transmitted under the condition that it contains no information indicating contents of transmission processing, such as information of data transfer rate. Therefore, the communication terminal has to process received data in the manner corresponding to all data transfer rates, and assumes the used data transfer rate from data obtained when the communication terminal processes received data. Then, the communication terminal selects data obtained when the communication terminal processes the received data in the manner corresponding to the estimated data transfer rate.
As the reception processing, the communication terminal implements a series of processing such as de-interleaving for rearranging the order of bit data of received data, de-repetition for returning a data amount of data obtained by the de-interleaving to the original data amount, Viterbi-decoding for decoding data obtained after convolutional-coding in the de-repetition and a CRC (cyclic redundancy check) for checking data obtained in the Viterbi-decoding by CRC codes.
When the communication terminal processes received data in the manner corresponding to all of the data transfer rates as described above, if the communication terminal repeats a series of the above-mentioned processing in response to all of the data transfer rates, then all received data should be repeatedly read out from a memory during the communication terminal processes received data in the manner corresponding to each data transfer rate before received data is de-interleaved, for example. As a consequence, a processing speed is lowered and a power consumption is increased unavoidably.
It is an object of the present invention to provide a data reception apparatus and a data reception method in which a processing speed may be increased and a power consumption may be lowered.
According to the present invention, there is provided a data reception apparatus for receiving data transmitted such that transmitted data of a data amount corresponding to a transfer rate on a communication line or transmitted data of an arbitrary data amount of a plurality of kinds of data amounts corresponding to xc2xdN times (N is an integer larger than 1) is used at every predetermined unit, transmitted data is directly interleaved and transmitted when a data amount of available transmitted data corresponds to a transfer rate on the communication line and each bit of transmitted data is repeated 2N1 times and the transmitted data is interleaved with the same pattern as that of the aforementioned interleaving when the data amount of the available transmitted data becomes corresponding to a transfer rate xc2xdN times the transfer rate on the communication line. This data reception apparatus comprises a de-interleave means for outputting fundamental data of a data amount corresponding to a transfer rate on a communication line by de-interleaving received data at every predetermined unit and a de-repetition means supplied with fundamental data of every predetermined unit and for sequentially outputting data corresponding to a plurality of kinds of data amounts by using the fundamental data at every predetrmined unit.
Initially, the de-repetition means outputs the fundamental data at every predetermined unit as it is. Then, the de-repetition means generates data of a data amount xc2xd times the data amount of the fundamental data by using the fundamental data and writes the data thus generated in a memory. Until data of a data amount corresponding to a transfer rate xc2xdNmaxxe2x88x921 times (Nmax is the maximum value of N) the transfer rate on the communication line is outputted, the de-repetition means repeats the steps of reading out data from the memory, outputting the data thus read out, generating data of a data amount xc2xd times the data amount of the read out data and writing the data thus generated in the memory. Finally, the de-repetition means reads out data of the data amount corresponding to the transfer rate xc2xdNmax times the transfer rate on the communication line from the memory, and outputs the data thus read out.
In the present invention, received data is stored in a memory within the de-interleave means, and the received data is de-interleaved by controlling the read address of this memory. The data obtained by this de-interleaving has a data amount corresponding to a transfer rate on a communication line, and is supplied to the de-petitition means as fundamental data.
The de-repetition means is operated as follows. Initially, the de-repetition means outputs the fundamental data as it is. Then, the de-repetition means generates data of a data amount xc2xd times the data amount of the fundamental data by using the fundamental data and writes the data thus generated in a memory. Until data of a data amount corresponding to a transfer rate xc2xdNmaxxe2x88x921 times the transfer rate on the communication line is outputted, the de-repetition means repeats the steps of reading out data from the memory, outputting the data thus read out, generating data of a data amount xc2xd times the data amount of the read out data by using the data thus read out and writing the data thus generated in the memory. Finally, the de-repetition means reads out data of the data amount corresponding to the transfer rate xc2xdNmax times the transfer rate on the communication line from the memory, and outputs the data thus read out.
This de-repetition means sequentially outputs the data corresponding to the data amounts of a plurality of kinds. The above-mentioned transmitted data is data encoded by convolutional codes, for example. The data corresponding to the data amounts of a plurality of kinds sequentially outputted from the de-repetition means is supplied to and decoded by a decoding means, e.g. a Viterbi decoder. Then, a data amount (transfer rate) of transmitted data is estimated from a plurality of decoded data and the like, and decoded data corresponding to the estimated data amount is finally selected and used.